docs: def _hasher_first_run(self, preimage):
          '''
          Invoke the backend on-demand, and check an expected hash result,
          then replace this first run with the new hasher method.
          This is a bit of a hacky way to minimize overhead on hash calls after this first one.
          '''
          new_hasher = self._backend.keccak256
          assert new_hasher(b'') == b"\xc5\xd2F\x01\x86\xf7#<\x92~}\xb2\xdc\xc7\x03\xc0\xe5\x00\xb6S\xca\x82';\x7b\xfa\xd8\x04]\x85\xa4p"  # noqa: E501
          self.hasher = new_hasher
          return new_hasher(preimage)